Home Cosmetic Science Talk Formulating General Off Topic Why polymerics and electrolytes don’t mix, By Pharma (in simple terms)

  • Why polymerics and electrolytes don’t mix, By Pharma (in simple terms)

    Posted by Graillotion on September 30, 2021 at 9:17 pm

    We all know that many of the polymeric emulsifiers and electrolytes don’t always make the best of friends.  But sometimes we just know they don’t mix, but are not fully aware of why they don’t.  
    We have an incredible asset on this forum, @Pharma , and he has taken time from his busy schedule to address this question, so we can know why…. and sleep better at night.  Thank you so much @Pharma , and I hope the rest of the members appreciate him like I do.  (If so….he likes ginger candies and dehydrated Mac nuts.  :D )  Here is his explanation that even a business major can understand.

    I don’t have a link which would explain it in layman’s terms.
    I can try to explain it: the incompatibility is mostly seen with charged
    (commonly anionics ergo negative charges) polymers. These work because
    the charges repel themselves like magnets of the same pole which leads
    to unfolding of the molecular strings. Like searches like: molecules
    tend to assemble with kin and the closest kin is themself like a snake
    head falling in love with its tail -> polymers precipitate unless they
    find motivation to unfold. A salt always contains negative and positive
    charges and one of these will be attracted by the charges of other
    molecules such as charged polymers. The salt atoms floating around the
    charged groups of the polymer string shield the polymers charges from
    each other, repulsion gets lost and the unfolded polymer collapses.
    High salt concentrations will also cause non-ionic polymers to
    precipitate like they precipitate anything in solution due to the
    salting-out effect.
    Most non-ionic emulsifiers are less effective than charged ones because
    the charge repelling effect is a very strong effect. Uncharged polymers
    unfold (form a ternary structure) due to their secondary structure. That
    secondary structure is a least energy/lowest strain conformation of the
    molecule. ‘Squeezing it together’ or bending it, say helical, structure
    requires only very little energy.

    OldPerry replied 2 years, 9 months ago 7 Members · 14 Replies
  • 14 Replies
  • Pharma

    Member
    October 1, 2021 at 7:05 pm
    You’re welcome :smiley:
    Darn, I think I have OCD… there’s a typo in my citation!
    …it, say helical, structure requires… should be …it, say helical structure,
    requires…

    Is this just exceptionally nitpicking or am I going Mac nuts? LoL!

  • Pattsi

    Member
    October 4, 2021 at 4:52 am

    Thank you @Graillotion and @Pharma

  • OldPerry

    Member
    October 4, 2021 at 8:55 pm

    Thank you all!  Can’t wait to have the Cosmetic Formulation Q&A with @Pharma  (coming later this month)

  • Graillotion

    Member
    October 4, 2021 at 9:09 pm

    Perry said:

    Thank you all!  Can’t wait to have the Cosmetic Formulation Q&A with @Pharma  (coming later this month)

    I was wondering when that was gonna happen!  Can’t wait.

  • Sponge

    Member
    October 7, 2021 at 4:22 pm

    Pharma (woo woo!), Pharma (woo woo!)

  • Sponge

    Member
    October 7, 2021 at 4:48 pm

    @Pharma, so repulsion falls under two main categories, steric and electrostatic, right? 

    What are the other [main] forms of stabilization and can you some them up in an equally beautiful paragraph?

     

  • Paprik

    Member
    October 7, 2021 at 6:04 pm

    Perry said:

    Thank you all!  Can’t wait to have the Cosmetic Formulation Q&A with @Pharma  (coming later this month)

    Wow, that is  a great news @Perry and @Pharma!! Thank you so much! :) 

  • Pharma

    Member
    October 7, 2021 at 7:43 pm

    Sponge said:

    @Pharma, so repulsion falls under two main categories, steric and electrostatic, right? 

    What are the other [main] forms of stabilization and can you some them up in an equally beautiful paragraph?

    Repulsion is mostly caused by electrostatic repulsion (measured as zeta potential in micellar emulsions), steric ‘don’t touch’ is called steric hindrance and works like porcupine quills versus predator.
    In case of emulsifiers, the former is achieved by using anionic or cationic emulsifiers whilst the latter is usually achieved with long hydrophilic head proups (e.g. PEGs, polyglyceryls). Hydrophobically modified polymers, gum Arabic, and milk proteins, oleosomes, modified silica, and other Pickering emulsifiers etc. also work, under others, by steric hindrance.
    These two stabilising strategies are mostly preventing oil droplet coalescence and partially also flocculation. Increasing viscosity of the outer phase (and the inner regarding coalescence but not flocculation) also helps and might be the number one used in current cosmetics.
    Ostwald ripening, a ‘slow motion’ instability which can easily go unnoticed in preliminary testing, is prevented by incorporating something soluble in the inner phase which is insoluble in the outer.
    Creaming and sedimentation are usually prevented by increased viscosity of the outer phase. Matching densities would also work.
    Most of these effects only work well with micellar emulsions and are usually only discussed in this context in text books. Many modern cosmetics are ‘ugly’ unpredictable messes of mixed type emulsions… called lamellar networks, alpha gels, or liquid crystals. Such structures often make up one part of the emulsion and are, combined with gelling agents, responsible for stability. Steric hindrance does work here, electrostatic repulsion partially works, Ostwald ripening and Pickering emulsifiers are of minor or no concern here. Matching densities and viscosity of the inner phase are also negligible or unpredictable (under others for the simple reason that there is not one inner phase).
    I know, not an equally beautiful paragraph but hopefully helps nonetheless.
  • Pattsi

    Member
    October 8, 2021 at 9:53 am

    Can’t wait for the session.

    I want to hear Pharma’s take on curcuminoid.

    Curcumin, Demethoxycurcumin
    and Bisdemethoxycurcumin in the Crude Curcuminoid
    Extract from Curcuma longa VS Tetrahydrodiferuloylmethane

    I have read Curcuma longa extract benefits in open wound but on intact skin I haven’t had any thing solid yet.

    I’m skeptical about Tetrahydrodiferuloylmethane.

    Any thought on Cassumunarin? Is it really good/special as papers from Thailand say it is?

    It’s a short session,  if it’s possible if you can point the direction to the study or book I can read further would be appreciated.

    @Perry - I missed the session with Mark, do I have any way to watch it, is it available on youtube?

  • Pharma

    Member
    October 8, 2021 at 7:35 pm
    @Pattsi One book? Maybe I can dig out the review my doctorat supervisor has published… there are thousands of papers on curcumin. Long story short, curcumin is too lipophilic to be of any use beyond topical effects (1-2 cell layers deep). Else, it would be a silver bullet.
    As far as I know, thetrahydrodiferuloylmethane is just a colourless substitute which looks good on the label.
    I don’t know anything about cassmunarin. Judging from its structure it’s even more lipophilic… I’d love to try it as spice, send some rhizomes pleeezz!
  • OldPerry

    Member
    October 8, 2021 at 8:59 pm

    @Pattsi - you can see Mark’s Q&A here. 
    https://vimeo.com/581168649/301fee65cc

  • Abdullah

    Member
    October 9, 2021 at 3:31 am

    @Perry thanks 

    Where we can watch all of these Q&As? 

  • Pattsi

    Member
    October 10, 2021 at 11:40 am

    Thank you @Pharma. I’m not sure I can send fresh rhizomes into Switzerland, let me check if it’s can be send as personal gift but I think the powdered one can.

    Thank you @Perry . 

  • OldPerry

    Member
    October 11, 2021 at 2:31 pm

    @Abdullah - We’ve got one coming up this week (although I’m doing it in conjunction with the IFSCC). See the pinned post up top.

    Typically, I post the previous Q&A in the sidebar of the forum. You can watch the one with Belinda right now.

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